In my experience I also feed the live bbs as soon as they hatch, but I would put the left overs in a cup into the fridge. This was because I would harvest them from the setup at the lab in uni so I didn't have a running hatchery at home. The bbs placed in the fridge would die in a few hours but because its cold, they would not rot for about 1-2 days. You can tell from their smell the minute they start rotting...
Anyways, the fry would take to the dead bbs shrimp from the fridge just as well. Since you plan to run a hatchery anyways, I would freeze your left over bbs because you never know, a batch might fail one night and you wont' have food the next day so its a good backup. I feed decap currently and it works as well but you need to pre-soak it for about 10 minutes because it expands...i wouldn't recommend putting it into an autofeeder.
Another thing you might want to consider is that light coloured and albino discus have a harder time raising fry because they don't have a lot or any dark pigments. When the fry become free-swimming they are attracted to dark shapes...Thus these parents might have a hard time keeping the fry from spreading around the tank and even going towards your other discus. I think you really need to place your pair in a seperate tank (with no dark objects or background in it) with the fry so that they have the best chance.